It is known that subjects presenting orthopedic problems involving the knee joint, but similarly also of other joints, such as the ankle or the elbow, above all in the case of injuries or as a result of a previous surgical operation, require the use of an orthopedic brace, or orthosis, designed to guarantee or control the hinge restraint function between the femur and the tibia or other articulated joint points, supporting stress which would otherwise be harmful for the joint.
The function of an orthosis is, in general, that of guaranteeing the relative immobilization or limitation of a joint affected by trauma, by arthrosis, by sprained ligaments or which has undergone a surgical operation.
Another use of orthoses is for the concomitant functional rehabilitation or re-education, wherein the orthosis can be used to reduce the load on the joint and reduce the pain, or can be used for prevention in cases of osteoporosis or bone weakness.
An orthosis usually comprises a rigid or soft frame, encircling the limb, designed to guarantee adequate harnessing of the joint in order to prevent the onset of stress on the ligaments or on the synovial membranes during walking by the injured and/or convalescent subject.
According to background art, the frame of an orthosis for joints, for example in the typical case of a knee brace, comprises means of restraint to the femur and the tibia and a section of connection of these means consisting of an articulated coupling positioned at the level of the knee.
The means of restraint usually consist of preformed bars that are fixed by means of suitable straps encircling both the femur and the tibia of the injured subject or fabric bands, straps or sleeves that make it possible to create a restraint between the ends of the mechanical articulated coupling and the limb.
The mechanical articulated coupling is positioned laterally with respect to the femur and the tibia, in the case of application, for example, to the leg. Thanks to its conformation consisting of 2 rotation centres relatively restrained to each other by toothed profiles, this articulated coupling follows the kinematic of the knee with good approximation.
A standard multicentre articulated coupling is a system consisting of two hinged bars, each one hinged to its own centre of rotation, wherein these centres of rotation are restrained parallel to each other and at a known distance.
In the standard multicentre articulated coupling, the two bars are connected to each other thanks to a circular toothed profile present on each bar, and this toothed profile places them in relative and synchronous motion with respect to each other.
In this articulated coupling, by definition, the rotation centres and the toothed profile, enable the bars to rotate only around two parallel axes and their rotation motion thus lies on one plane.
Among the problems that can affect a joint are varus and valgus deformities, which constitute skeletal abnormalities causing axial deviations of the limb, wherein the skeletal segments, situated distally with respect to the section in which the deviation occurs, are in the abnormal position of abduction in valgus deformities and adduction in varus deformities, that is to say in the first case farther away and in the second case closer with respect to the mid-line of the body.
The most typical case concerns the knees which, if suffering from a varus deformity, tend to be spread apart towards the outside of the body with respect to the undeformed axis of the limb. Vice versa, in cases of valgus deformities, the knees tend to point inwards and be closer to each other.
In both of the cases of deformity described above, the subject tends to experience greater difficulty in walking the narrower the open obtuse angle is inwards in the case of a varus deformity or outwards in the case of a valgus deformity.
There are various known solutions to this problem, for example through the use of special knee braces or orthoses aimed at correcting the misalignment of the joint, generally through the use of shims of various types inserted inside the brace close to the lateral thrust area to be fitted on the articulated coupling.
More in general, traditional background art orthopedic braces are, by definition, made using rotation centres that enable the bars to rotate only on one plane around two parallel axes, preventing the creation of lateral thrusts to correct problems such as those relative to varus and valgus deformities, which are achieved by using special filling elements such as spacers or shims of various kinds.
While clinically and at least partially resolving limb deformities, the solutions proposed so far are not without drawbacks substantially connected with the use of the orthosis.
One problem is represented by the fact that these braces are difficult to adjust, especially when in use; in fact, a gradual recovery of the limb requires continuous measurement of the obtuse angle between femur and tibia, in the case of the knee, with consequent adaptation of the orthosis, particularly as regards its rigid frame.
Another drawback is represented by the fact that these braces are sometimes difficult to wear as they consist of several reciprocally connected portions that can be fixed by any appropriate means of temporary blocking.
The document U.S. Pat. No. 4,599,998 describes an articulated coupling for orthopedic braces comprising a pair of bars rotating around respective fixed pins mounted on a platform. The ends of these bars are toothed and engage with a toothed cursor mounted on a support fixed to the platform and translatable along an axis parallel to the plane of the platform.